Telemetry refers to the technology used by remote sources such as space vehicles to measure and transmit data to ground-based receiving stations, and vice versa. Within a telemetry system, the transponder is a critical device which picks up and automatically responds to an incoming signal. A transponder contains the processing capability, including error checking functions, to ensure the reliability of the data.
With the associated hardware necessary for a satellite to interface with the transponder, a typical NASA telemetry system costs $5 to $10 million dollars per satellite.
A primary cost associated with development and customization of transponders and telemetry systems is the configuration and development of error checking components. Specific error checking protocols are required for various telemetry applications. Error checking is a “modular function,” that is carried out independently of other processing activities.
All error checking protocols must comply with Ground Network and Consultative Committee for Space Data System (CCSDS) protocols which are required for each telemetry application.
Because both error checking functions and CCSDS protocols are modular, hardware and software for error checking theoretically may be inserted or removed from the data stream telemetry requirements.
Examples of current telemetry system error checking protocols include Reed Solomon (forward error correction), BCH (error detection only), Pseudo-Randomization (required for operation), turbo codes, convolutional code (1/2, 7/8), Virterbi, auto-ranging, encryption, and cyclic redundancy check (CRC).
An additional problem known in the art is the need for strict quality control protocols or “prequalification” of each component used by NASA. The qualification process is extremely costly and generally requires that a new device be tested in a NASA lab or have been previously used in flight. Components meeting this standard are referred to, in the art, as “prequalified” devices.
The qualification process limits the availability of transponders designed to interface with rapidly evolving and diverse telemetry systems including lunar missions and missions to Mars, military intelligence, wireless internet, cellular telephones, climate change studies, and emergency services such as fire, ambulance and police.